Laminating glue solutions and extender compositions therefor and process for preparing same



United States Patent LAMINATING GLUE SOLUTIONS AND EXTENDER COMPOSITIONSTHEREFOR AND PROCESS FOR This invention relates to laminating gluesolutions of superior application and bonding qualities, andparticularly to glue solutions having the propertiesrequired for highspeed machine applicationasemployed in the plywood fabricating industry.It also relates to novel extender compositions for sale to and'use bysaid industry for incorporation in aqueous resin glue emulsions forproducing such glue solutions.

As set forth in my copending applications SeriahNo.

425,05 1 now U.S. Patent 3,017,303 and SeriallNo. 643;

5 01, filed March- 4, 1957; and now abandoned, having been replacedby'SerialNo. 39,812, I have heretoforediscoveredthat extendercompositions composed of vegetable shell flour containing .anaddition ofa minor amount of, a finely divided, extracted lignin, either inunoxidizedform or in oxidized form, can improve the properties ofphenolic resin and other glue solutions when added there to, byincreasing the viscosity of the solution and decreasing the penetrationof the glue into soft or porous surf-aces of core woods. The addition ofthe extracted lignin in oxidized form produces exceptionally high gradeplywood of the most varied construction (as to both thickness and numberof veneers), evenwhen the core Theoverall object of the invention is toprovide novel adhesive solutions containing new extender compositions,possessing to a uniquedegree all of the desirable properties forproducing plywood of consistently high quality both asto strength andwater-resistance, from all grades of wood including soft wood andnon-uniform or rough cores, which properties include high glue viscosityand viscosity stability, uniform transfer.and spreading from theapplicator rolls, stability of film during assembly and lack ofexcessive penetration into wood pores.

Broadly expressed the extender compositions of the present invention arebasically composed of a vegetable shell flour extender, and minoramounts of an extracted lignin preferably wholly (or at least in part)in oxidized form, and of a non-fibrous, high-temperature, high-pressure,hydrolyzation-degradation residue of a vegetable shell material.

The vegetable shell flour used is exemplified by nut shells, as those ofEnglish and black walnuts and pecans, fruit pit shells, as thoseofapricots and peaches.

The extracted lignin component hereinbefore mentioned is exemplified'by-the so-called alkali lignin-produced as a by-product from woodpulping processes employing alkali, the most common procedure beingknown as the kraft process. Extracted lignins produced by-biological andselective solvent action, as well as thoseprepared by chemical actioncan be employed, and in common the lignin'products are free orsubstantially free of combined cellulosic constituents, woodsugars andother 3,093,695 Patented June 11, 1963 products of the wood or otherligno-cel-lulosic materials from which the lignin is obtained, and suchextracted lignins are all soluble in alkali, apparently producing sodiumlignate.

The lignin components of the oxidized lignins of applicants compositionsare both acid-insoluble and water-insoluble and are referred to as beingextracted, for they are products which have been separated from the woodor other ligno-cell'ulose material. Sulfonic acid derivatives, or ligninsulfonates, such as are obtained in the Sulfite process of paperproduction being acid and watersoluble are not included within the scopeof said term. Only through the use of lignin in extracted form can thequality and the performance of the adhesive compositions of theinvention be attained and maintained. To produce commercially acceptableresults, experience has shown that it is essential that not only mustthe lignocellulose extender be of known constitution and uniformcharacter, but also the oxidized lignin component must be of a definiteand known quality.

Suitable extracted lignins are described in the booklet entitled Indulinissued by the West Virginia Pulp and Paper 00., Charleston, WestVirginia (1951). Other suitable lignin products contemplated aredisclosed in the booklet entitled Commercial Lignins by Robert S. Ariesand Arthur Pollak issued by the Northeastern Wood Utilization Council,New Haven, Connecticut (1949).

The oxidized lignin preferably used in the practice of the invention maybe obtained by oxidation in neutral solution, in alkaline solution or,under certain circumstances, in an acid solution, but it can also beaccomplished electrolytically or by enzymatic action. Practicallyconsidered, the oxidation is accomplished under aqueous alkalineconditions simply by introducing oxygen into ing heating to the settingtemperature and the prevention of excessive fiowinto the poresconstitutes the primary advantage of the presence of the extractedlignin in the.

oxidized condition. Oxidation to an extent providing any appreciabledegree of viscosity increase in the aqueous suspension improves theretention at the glue line.

As is indicated in the hereinbefore mentioned Indulin booklet (page'18), the oxidation may be eifected satistactorily by introducing oxygeninto an alkaline solution in water or other solvent until about 1 to 7mols of oxygen per mol of lignin (M.W. 840) has taken up. The alkalinitymaybe imparted by the addition of any alkali, suitably sodium hydroxide,in a quantity of from 1-16 mols per mol of extracted lignin. As is alsopointed out in said booklet, the rate and extent of oxygen absorption isincreased with increasing alkali content. If the oxidation is continuedtoo long, the gel is advanced in structure too far, and drying andfurther processing becomes very difii'cu'ltorpractically impossible.Thus it is the practical problem of handling which limits thepermissible amount of oxidation. In all instances, the oxidation isterminated, of course, before any drastic break down of the ligninmolecules occurs and destroys their viscosity-imparting qualities.

Anoxidized lignin found particularly effective was produced byconcentrating a spent black cooking liquor obtained from a kraft paperprocess to provide a liquid containing 18 to 20% solids. Cooled carbondioxide gas was then bubbled through the concentrated solution whilesaid solution was being continuously circulated, to precipitate thelignin. Upon completion of the precipitation, the carbonated liquor washeated at a temperature close to boiling to bring about coagulation ofthe lignin. After being cooled, the coagulated liquor was separated byfiltration and the lignin was purified by washing.

The washed cake was then repulped in water and sufficient sodiumhydroxide was added to adjust the pH of the suspension to an approximatevalue of 9. Thereupon air was blown into the solution during vigorousagita tion until oxidation had occurred, this result being determined bythe viscosity increase of the suspension. After oxidation, thesuspension was concentrated, filtered and dried, this latter resultpreferably being obtained by spray drying. The final product thusobtained can be described as a technically pure, oxidized, extractedalkali lignin.

The completion of the oxidation step in the abovedescribed process wasdetermined by a standardized test involving adding 60 grams of theoxidized product and 300 grams of distilled water to a 600 cc. beaker.The mixture in the beaker was then stirred for three minutes with anelectric stirrer. Next a sodium hydroxide solution made up of 50 gramswater and 2 grams of solid sodium hydroxide was added. The resultingmixture was then electrically stirred for a period of five minutes.Thereupon, the mass was adjusted to a temperature of 77 F. and allowedto stand at this temperature for fifteen minutes. At the end of thisperiod, the viscosity was measured with a Brookfield viscosimeterequipped with a No. 4 spindle, at 6 rpm. The reading was 90,000centipoises.

Using this test for the determination and control of the oxidation,oxidized extracted lignins operable for the purposes of the presentinvention have revealed viscosities as low as 5000 centipoises andviscosities much higher than the 90,000 centipoises reading.

In addition to the above defined oxidized, extracted alkali lignin, theinvention contemplates the use of oxidized, extracted alkali ligninscontaining some thiolignin due to the presence of SH groups introducedinto the lignin molecules by the action of sodium sulfide during cookingprocesses used in preparing paper by the sulfide process.

The degradation residues used in the practice of the invention may befurther described as the solid or waterinsoluble portion of vegetableshell materials resulting from the heating of such materials underpressure in the presence of water under sufficiently severe conditionsto cause hydrolysis of the hydrolyzable components, which components aresubsequently removed in and with the water. The vegetable shellmaterials are exemplified by nut shells as walnut, pecan and almondshells, endocarps of drupes such as peach and apricot pits and othernonfibrous (or mildly fibrous), non-capillary shell materials.

The degradation residues may be obtained, for example, by mixing theshell material in finely divided form with water and subjecting themixture to heating under steam pressure of about 100 pounds (temperatureof about 287 for at least one hour and preferably for approximatelythree hours, then filtering and washing with water to remove thewater-soluble decomposition products from the desired insoluble residue,and drying, grinding and classifying the residue to provide a dry,finely divided hydrolyzation-degradation residue, suitably of 200 mesh.The residue is non-fibrous or practically nonfibrous in structure. Thetemperature and pressure may be raised somewhat and the time variedbetween about 1 and hours. Suitable products will generally be obtained.Experimentation reveals that conditions for producing products of highperformance characteristics can be determined merely by testing theviscosity-imparting capacity of test samples.

Relatively large quantities of this degradation residue may beincorporated in the extender compositions, and hence in the gluesolutions, in relation to the amount of synthetic resin present, withoutadversely reducing the water resistance of the bond or the sheerstrength of the plywood produced with such glue. Under ordinaryconditions from 10 to 30% by weight of the degradation residue can beemployed in the extender compositions and these proportions ordinarilywill impart thixotropy to the glue mixes. The amount of the lignincomponent in such composition can be varied within a wide range, thePractical range usually being 5 to 50% and the optimum range 15 to 20%,based on the weight of the compositions of the three components.

The three components to be combined to form the extender composition maybe blended merely by mixing the same in finely divided form in astandard ribbon type blender until a homogeneous product is obtained.

The extender compositions hereinbefore described can be employed veryadvantageously with plywood glue solutions of conventional types whichare generally aqueous alkaline emulsions of artificial resins. Undersome conditions, the amount of alkali already in the glue solution issuflicient, but ordinarily the addition of caustic alkali or sodiumcarbonate in amounts somewhat in excess of that which reacts with theextender components improves the bonding quality of the glue solution.Although 5% of either or both of said alkali materials (calculated inrelation to the amount of extender composition present) may besuflicient in some glue solutions, the amount may be increased to 15 to20% or more, as to each of said alkaline materials.

Plywood fabricators obtaining the extender compositions hereinbeforedescribed can produce the adhesive solutions of the invention bygradually adding such compositions to the water to be used for dilutionof the resin to which has already been added the sodium hydroxide orother caustic alkali ordinarily employed, and the mixture is agitateduntil uniform fluidity is obtained, 20 to 30 minutes usually beingsuflicient. When sodium carbonate is to be employed, it is preferablyintroduced immediately after the extender composition has been added.The application of heat is not ordinarily required. Upon completion ofthe mixing operation the resin glue solution is added and the mass isagain agitated for a few minutes or until a homogeneous mass isobtained.

The resin glue solutions in which the extender compositions areparticularly effective may be described as aqueous colloidal solutionsof thermosetting aldehydic resin glues. Such solutions are produced andsold by several companies (usually in solutions of 40-50 resin solidscontent) and their production constitutes no part of the presentinvention. The resins used include condensation products of phenoliccompounds such as phenol, cresol, and resorcinol, or amino-compoundssuch as urea and melamine with an aldehyde, such as formaldehyde andacetaldehyde.

In the glue solutions produced in accordance with the present invention,conventional ratios of resin to extender composition to water can beemployed. When conventional phenolic resin glue aqueous emulsions (about40- 50% solids) are employed the weight ratio of resin to extender towater is, suitably, 5/ l/ 1.75. The ratio of extender and water in thecompositions can be greatly increased to provide solutions having ratiosof as high as 5/4/ 7, and such glue solutions are economicallyacceptable for the production of plywood of one type or another, but allof high grade.

In accordance with a modification of the invention, the extendercompositions and adhesive solutions contain in addition to the oxidizedlignin, also some plain or unoxidized extracted lignin, all or part ofwhich may be in the form of sodium lignate, for example, a material suchas Indulin C. The unoxidized extracted lignin will ordinarily replacepart of the oxidized extracted lignin in the.

compositions herein defined. The amount of the oxidized lignin which canbe replaced by unoxidized lignin depends upon a number of factorsincluding the grade or porosity of the wood and viscosity requirementsof-the glue solution. Displacement in greatest amounts is possible whenplywood products of thin construction, as 7 inch, are being produced.From to 75% of the oxidized lignin may be replaced by the unoxidizedlignin and/ or sodium lignate), and when thin plywoodis fabricated, thedisplacement may reach as high as 90%.

Ina special embodiment of the invention leading to the production ofparticularly high grade plywood, a minor or small amount of epoxy resinis incorporated in the compositions hereinbefore defined. The epoxyresin need be present in an amountas little as .4 to 1%, by weight, ofthe phenolic resin content to impartworth-while im-. provement inquality of the bond. Amounts as high as 20% can be used, but such higheramounts are now economically unfeasible. The. epoxy resin is preferablyintroduced by preliminarily coating the shell flour particles with 2 to7% resin, but such resin may be mixed in solu-. tion form with thephenolic resin solution. The epoxy resin used can be any of thecommercial adhesive products such as may be produced by reactingbis-phenols or other polyhydroxy compounds with either of the usualchlorohydrins, epichlorohydrin or dichlorohydrin, specific examples ofthe same being disclosed .in the hereinbefore mentioned copendingapplication Serial No. 643,501. Other epoxy resins utilizable aredisclosed in the book entitled Epoxy Resins by HenryLee and KrisNeville.

published by the McGraw-Hill Book Company, Inc;, New York, in 1957.

Example I described in the specification, were added to 80 parts of -325mesh English walnut shell flour and blendedin a dry mixer for about twominutes, a dry mix being obtained.

Example 2 Using the same materials described in Example 1 but indifferent proportions, 16 parts each of the oxidized, extracted ligninand of the degradation residue were added to 68 parts of the Englishwalnut shell flour and blended to obtain a dry mixture.

Example 3 An adhesive solution for use in producing plywood was preparedby adding 115 parts of the extender composition described in Example 1to 175 parts of water in/ which 30 parts of sodium hydroxide (50%aqueous solution) had been dissolved. Thereupon parts of sodiumcarbonate were added and the mixture stirred for minutes. Next 500 partsof a conventional commercially obtainable phenol-formaldehydeplywood-glue in aqueous alkaline solution (viscosity G; solids content,40.8%) were added and the resulting mass stirred for about five minutes.A high viscosity, free-flowing homogeneous mass was obtained.

Example 4 The procedures of Examples 2 'and 3 were repeated except thatthe walnut shell flour used was one which had been coated with 5% of anepoxy resin of conventional character. produced by the reaction ofepichlorohydrin and 2,2 bis (parahydroxy phenol) propane in aqueousalkaline solution.

Example 5 The procedure of Example 1 was repeated with the 6 a changethat the amount of oxidized lignin was reduced to 10 parts and wassupplemented by the addition of 10 parts of extracted lignin inunoxidized form, half of which was sodium lignate.

The components of the extender compositions and the glue solutionsherein referred to, other than the degradation product component aredescribed in more detail along with additional examples, procedures andadvantages in the hereinbefore mentioned prior applications.

The glue solutions of the present invention have several outstandingadvantages:

They have an exceptionally high viscosity, leading to more exact anduniform quantities of glue spread in the film applied to the core woodand to greater resistance to the centrifugal force of the rapidlyrevolving spreader rolls of the glue applying machine, which force has atendency to throw glue solution off the rolls. After the glue solutionhas flowed over the wood surfaces in an even spread, it (1) ceases toflow and assumes a limpid gel structure, thixotropic in character, andthus (2) does not penetrate too deeply into the wood even though thewood may be quite porous in character, (3) does not lose too much waterby evaporation and (4) retains its binding qualities over a substantialperiod, providing long assembly time life.

This application is a continuation-in-part of my copending application.Serial No. 643,536 filed March 4, 1957, and now abandoned.

It should be understood that the invention is not limited to the exactcompounds, proportions, procedures and conditions herein described butthat it extends to all equivalents which will occur to those skilled inthe art uponconsideration of the scope of the claims I claim:

1. A composition of matter for adding to and improving the viscosity,wood penetration, bonding and other properties of plywood adhesive andother laminating adhesive solutions which comprises, a homogeneousmixture of a vegetable shell flour extender and minor amounts infinely-divided form of an extracted lignin in oxidized condition andcontaining about 1 to 7 mols of added oxygen per mol of lignin, and of awater-insoluble, nonfibrous, high-temperature, high-pressurehydrolyzationdegradation residue of a vegetable shell material degradedby an amount at least equal to that obtained by heating such material infinely divided form in an aqueous appended hereto.

medium under about pounds steam pressure for at least one hour.

2. The composition of claim 1 wherein the degradation residue is of nutshells.

3. The composition of claim 1 wherein the degradation residue is ofpeach pits.

4. The composition of claim 1 wherein the degradation residue is offruit pit shells.

5. A composition of matter for adding to and improving the viscosity,wood penetration, bonding and other properties of plywood adhesive andother laminating adhesive solutions which comprises, a homogeneousmixture of a vegetable shell-flour extender and minor amounts infinely-divided form of an extracted lignin oxidized so as to containabout 1 to 7 mols of added oxygen per mol of lignin, and of awater-insoluble, degradation solids residue resulting from hightemperature and pressure hy-drolyzation of endocarps of a drupe, whichendocarps have been degraded by an amount at least equal to thatobtained by heating them in finely divided form in an aqueous mediumunder about 100 pounds steam pressure for at least one hour.

6. Extender-modifier composition for glue solutions which comprises, ahomogeneous mixture of a vegetable shell 'flour extender and minoramounts in finely-divided form of an extracted lignin in oxidizedcondition and containing about 1 to 7 mols of added oxygen per mol oflignin, of an extracted lignin and of a Water-insoluble, non-fibrous,high-temperature, high-pressure hydrolyzadon-degradation residue of avegetable shell material degraded by an amount at least equal to thatobtained by heating such material in finely divided form in an aqueousmedium under about 100 pounds steam pressure for at least one hour.

7. Extender-modifier composition for glue solutions which comprises, ahomogeneous mixture of a vegetable shell flour extender, the particlesof which are coated with an epoxy resin derived by the reaction of apolyhydroxy hydrocarbon with a compound selected from the groupconsisting of epichlorohydrin and dichlorohydrin and containing freeepoxy groups, and minor amounts in finely-divided form of an extractedlignin oxidized so as to contain about 1 to 7 mols of added oxygen permol of lignin, and of a water-insoluble, nonfibrous, high-temperature,high-pressure hydrolyzationdegradation residue of a vegetable shellmaterial degraded by an amount at least equal to that obtained byheating such material in finely divided form in an aqueous medium underabout 100 pounds steam pressure for at least one hour.

8. Plywood-, and laminating-adhesive solutions which comprise, athermosetting aldehydic resin glue selected from the group consisting ofphenolic-aldehyde resins and amino-aldehyde resins, in aqueous alkalinecolloidal solution to which has been added, a vegetable shell flourextender and minor amounts in finely-divided form of an extracted ligninoxidized so as to contain about 1 to 7 mols of added oxygen per mol oflignin, and of a waterinsoluble, non-fibrous, high-temperature,high-pressure hydrolyzadon-degradation residue of a vegetable shellmaterial degraded by an amount at least equal to that obtained byheating such material in finely divided form in an aqueous medium underabout 100 pounds steam pressure for at least one hour.

9. Plywood, and laminating-adhesive solutions which comprise, athermosetting aldehydic resin glue selected from the group consisting ofphenolic-aldehyde resins and amino-aldehyde resins, in aqueous alkalinecolloidal solution to which has been added, a vegetable shell flourextender and minor amounts in finely-divided form of an extracted ligninoxidized so as to contain about 1 to 7 mols of added oxygen per mol oflignin, and of a water-insoluble, non-fibrous, high-temperature,highpressure hydrolyzation-degradation residue of nut shells degraded byan amount at least equal to that obtained by heating such shells infinely divided form in an aqueous medium under about 100 pounds steampressure for at least one hour.

10. Plywood-, and laminating-adhesive solutions which comprise athermosetting aldehydic resin glue selected from the group consisting ofphenolic-aldehyde resins and amino-aldehyde resins in aqueous alkalinecolloidal solution containing therein a vegetable shell flour extenderand minor amounts of an alkali-dissolved, extracted lignin in oxidizedcondition and containing about 1 to 7 mols of added oxygen per mol oflignin and of a waterinsoluble, non-fibrous, high-temperature,high-pressure hydrolyzation-degradation residue of a vegetable shellmaterial degraded by an amount at least equal to that obtained byheating such material in finely divided form in an aqueous medium underabout 100 pounds steam pressure for at least one hour.

11. Plywood-, and laminating-adhesive solutions which comprise, athermosetting aldehydic resin glue selected from the group consisting ofphenolic-aldehyde resins and amino-aldehyde resins, in aqueous alkalinecolloidal solution, a vegetable shell flour extender and a minor amountof sodium lignate, the lignin component of which is an extracted ligninresulting from the kraft paper pulp process and which is oxidized so asto contain about 1 to 7 mols of added oxygen per mol of lignin, and aminor amount of a water-insoluble, non-fibrous, hightemperature,high-pressure hydrolyzation-degradation residue of a vegetable shellmaterial degraded by an amount 8 at least equal to that obtained byheating such material in finely divided form in an aqueous medium underabout pounds steam pressure for at least one hour.

12. Plywood-, and laminating-adhesive solutions which comprise, athermosetting aldehydic resin glue selected from the group consisting ofphenolic-aldehyde resins and amino-aldehyde resins, in aqueous alkalinecolloidal solution containing therein in minor amounts a vegetable shellflour extender, an epoxy resin derived by the reaction of a polyhydroxyhydrocarbon with a compound selected from the group consisting ofepichlorohydrin and dichlorohydrin and having free epoxy groups, anextracted lignin oxidized so as to contain about 1 to 7 mols of addedoxygen per mol of lignin, and a water-insoluble, nonfibrous,high-temperature, high-pressure hydrolyzationdegradation residue of avegetable shell material degraded by an amount at least equal to thatobtained by heating such material in finely divided form in an aqueousmedium under about 100 pounds steam pressure for at least one hour.

13. A process for improving the qualities of plywood-, andlaminating-adhesive solutions containing a thermosetting aldehydic resinglue selected from the group consisting of phenolic-aldehyde resins andamino-aldehyde resins, in aqueous alkaline colloidal solution whichcomprises adding thereto a vegetable shell flour extender and minoramounts in finely-divided form of an extracted lignin oxidized so as tocontain about 1 to 7 mols of added oxygen per mol of lignin, and of awater-insoluble, non-fibrous, high-temperature, high-pressurehydrolyzation-degradation residue of a vegetable shell material degradedby an amount at least equal to that obtained by heating such material infinely divided form in an aqueous medium under about 100 pounds steampressure for at least one hour.

14. A process for improving the qualities of plywood-, andlaminating-adhesive solutions containing a thermosetting aldehydic resinglue selected from the group consisting of phenolic-aldehyde resins andamino-aldehyde resins, in aqueous alkaline colloidal solution whichcomprises adding thereto a vegetable shell flour extender with a smallamount of an epoxy resin derived by the reaction of a polyhydroxyhydrocarbon with a compound selected from the group consisting ofepichlorohydrin and dichlorohydrin and having free epoxy groups andminor amounts in finely-divided form of an extracted lignin oxidized soas to contain about 1 to 7 mols of added oxygen per mol of lignin, andof a water-insoluble, nonfibrous, high-temperature, high-pressurehydrolyzationdegradation solids residue of endocarps of a drupe degradedby an amount at least equal to that obtained by heating such drupes infinely divided form in an aqueous medium under about 100 pounds steampressure for at least one hour.

15. An extender-modifier composition for plywood glue solutions or thelike, comprising a homogeneous mixture of a major proportion of walnutshell flour, about 10 to 30% by weight of a water-insolublesubstantially non-fibrous solid residue of the treatment of finelydivided nut shells in an aqueous medium under steam pressure of at leastabout 100 psi. for at least 1 hour, said residue being finely divided sothat substantially all of its particles are of minus 200 mesh in size,and about 5 to 20% by weight of finely divided extracted lignin at least10% of which is oxidized extracted lignin containing about 1 to 7 molsof added oxygen per mol of lignin.

References Cited in the file of this patent UNITED STATES PATENTS2,161,748 Samaras et al. June 6, 1939 2,506,486 Bender et al. May 2,1950 2,669,522 Othmer et al. Feb. 16, 1954 2,781,328 Ayers et al. Feb.12, 1957 2,878,197 Baxter et al. Mar. 17, 1959

8. PLYWOOD-, AND LAMINATING-ADHESIVE SOLUTIONS WHICH COMPRISE, ATHERMOSETTING ALDEHYDIC RESIN GLUE SELECTED FROM THE GROUP CONSISTING OFPHENOLIC-ALDEHYDE RESINS AND AMINO-ALDEHYDE RESINS, IN AQUEOUS ALKALINECOLLOIDAL SOLUTION TO WHICH HAS BEEN ADDED, A VEGETABLE SHELL FOUREXTENDER AND MINOR AMOUNTS IN FINELY-DIVIDED FORM OF AN EXTRACTED LIGNINOXIDED SO AS TO CONTAIN ABOUT 1 TO 7 MOLS OF ADDED OXYGEN PER MOL OFLIGNIN, AND OF A WATERINSOLUBLE, NON-FIBROUS, HIGH-TEMPERATURE,HIGH-PRESSURE HYDROLYZATION-DEGRADATION RESIDUE OF A VEGETABLE SHELLMATERIAL DEGRADED BY AN AMOUNT AT LEAST EQUAL TO THAT OBTAINED BYHEATING SUCH MATERIAL IN FINELY DIVIDED FORM IN AN AQUEOUS MEDIUM MEDIUMUNDER ABOUT 100 POUNDS STEAM PRESSURE FOR AT LEAST ONE HOUR.